Limonene is an aromatic cannabis terpene produced in the flower’s resin glands. In isolation, it’s commonly associated with fruity, citrus aromas, and it’s found in many everyday items like fruit rinds, cosmetics, and cleaning products.
Terpenes are fragrant oils secreted alongside cannabinoids like THC and CBD, and these terpenes not only determine the smell of a cannabis strain, they may also modify its effects.
While limonene is often assumed to be abundant in strains that smell like lemon, this isn’t always the case. When seeking strains high in limonene, you’ll need to find lab-tested products to know that the strain you’re buying is in fact limonene-packed.
Whereas THC typically makes up 10-30% of a flower’s dry weight, limonene occurs in trace amounts, generally less than 2%. Romatherapy, mainly through the use of diffusers, has long lauded the mood-boosting effects of limonene– positioning it as both an anxiolytic (anti-anxiety) and anti-depressant.
This terpene is not limited by its form factor, though. It is used in food, beverages, perfumes, soaps, cleaners, and can even strip paint. While high concentrations can lead to skin irritation, proper dilution makes limonene safe.
Chemists can convert limonene into carvone. Remarkably, modern chemistry allows for the transformation of this citrus flavor to mint. Carvone is contained in spearmint and also found in trace amounts in cannabis.
The anti-cancer effects of limonene have been extensively studied.
Research has indicated this terpene may be specifically helpful for:
- Skin tumorigenesis
- Squamous cell carcinoma
- Prostate cancer
- Pancreatic cancer
- Breast cancer
- Liver cancer
- Lung cancer
Since the citrusy terpene has been shown to accumulate in fatty tissue, it makes sense that it has been useful for the prevention and treatment of breast cancer and other tumors found in fatty regions.
The anti-inflammatory effects of this organic compound are well documented, especially in its ability to help curb colitis— a phenomenon that seems to occur due to its ability to suppress the production of pro-inflammatory cytokines.
Like with other hydrocarbons, D-limonene also has antioxidant properties, stemming from its impact on complex signaling pathways. These antioxidant properties help with the immune system by assisting with the removal of free radicals throughout the body.
This anti-oxidant terpene may even also reduce hunger and appetite through its aroma alone. It may also help diabetics with high blood sugar levels. Patients who have experienced a stroke or hypertension may also find benefits from limonene since it can decrease systolic blood pressure.
Confirming years of anecdotes, this pungent compound has also been shown to help with anxiety relief through both inhalation (aromatherapy) and oral administrations. Adding to relaxation, it has also been shown to have muscle relaxant properties. It has also been shown to help with other disorders that are classically associated with stress like gastric disorders including heartburn and gastric acid reflux.
Limonene has also been shown to be a highly effective anti-viral– reducing viral infectivity by 100%, an efficient anti-fungal, and anti-bacterial. Gives a whole new meaning to the lemon-fresh-clean smell, huh?
The essential oil of a limonene-containing-fruit (Amomum tsaoko) bas been shown to be an insect repellant, even though other research has shown that it may attract insects.
When inhaled, like with cannabis, this terpene may help with asthma. Don’t get too overzealous on that one, though; terpenes such as limonene, alpha-pinene, and isoprene can cause irritation to the upper respiratory system.
A portion of the UK population is allergic to limonene and linalool when applied to the skin. Terpenes can also degrade to other harmful chemicals under high temperatures. Readers are urged to caution with dabbing and vaping cannabis with excess terpenes.
This laundry list of limonene benefits is extended to cannabis strains high in limonene and helps to explain why cannabis has been widely regarded as a panacea, qualifying as an effective treatment for a whole host of medical conditions. There are 100s of other terpenes found in the cannabis plant, each with their own medical efficacy. These terpenes compliment the other cannabinoids to create a synergistic effect known as the entourage effect. Be sure to read up on the other terpenes found in cannabis and learn how cannabis can be used to treat hundreds of conditions.
Limonene’s potential effects and benefits
The aromatherapeutic effects noted above also help describe what this terpene brings to the cannabis experience. Overall, limonene helps promote an uplifted and elevating mood, free of anxiety, as evidenced by the strains that strongly express it.
Despite limonene’s potential therapeutic benefits, little is known about how it works in the brain and body, and what doses are required to achieve these benefits. In many of the limonene studies to date, high doses were used—much higher than amounts found in cannabis. More cannabis-focused research is needed, but studies on limonene so far have shown potential in the following applications:
- Elevated mood
- Stress relief
- Antifungal properties
- Antibacterial properties
- May help relieve heartburn and gastric reflux
- Improves absorption of other terpenes and chemicals by way of the skin, mucous membranes, and digestive tract
There’s also promising evidence for limonene’s anti-tumor effects. In lab rodents, limonene inhibited the growth of skin and mammary tumors. These studies were followed up with a Phase I human clinical trial which found that limonene was somewhat effective at reducing breast cancer tumor growth for nearly a year. Later studies found that daily limonene supplementation for 2-6 weeks silenced a protein that promotes breast cancer tumor growth, suggesting that daily limonene consumption may inhibit the growth and spread of breast tumors.
Additional reports have revealed benefits of limonene in laboratory models of lung cancer and brain cancer by causing tumor cell death. But like limonene’s benefits in breast cancer, high doses are likely needed beyond what may be present in cannabis alone. It’s unknown, however, whether the presence of certain cannabinoids extends limonene’s anti-cancer effects. Currently, there is not nearly enough evidence to conclude that cannabis products high in limonene will be effective as cancer treatments in humans.
Future research on limonene
It remains unclear how limonene achieves its therapeutic effects. Inhalation of limonene vapor increases serotonin and dopamine levels in key regions of the brain that are associated with anxiety, depression, and OCD. Does limonene merely stimulate the brain’s olfactory system, or is it directly affecting brain cells themselves? We don’t yet know.
Unlike some of the other terpenes that have well-defined brain targets, such as linalool and b-caryophyllene, limonene’s targets remain unclear.
By better understanding limonene’s targets in the brain and body, scientists may help direct users towards strains or products where limonene’s therapeutic benefits are optimized by a particular cannabinoid and terpene profile.